1. Field of the Invention
The present invention generally relates to automobile grilles positioned at the front end of an automobile. More specifically, this invention relates to an automobile grille having a decorative metallic plating, wherein the decorative metallic plating is selectively deposited on the grille so as to optimize the flexural properties of the grille. The grille of this invention is particularly well suited for use with impact-absorbing bumpers which automatically rebound from a frontal impact.
2. Description of the Prior Art
Automobile grilles have generally evolved from what once was primarily a barrier to protect an automobile's radiator to its present status as primarily a decorative feature, though also often serving as the primary source of ventilation to the radiator. Accordingly, the earlier grilles were formed from metal so as to have adequate strength to deflect objects from hitting the radiator. Today, the role of the automobile grille as a barrier has been largely supplanted by modern practices which position the radiator such that it is protected by other means. For styling purposes, the automobile grille is still present on most modern automobiles, though generally formed from plastic to save weight.
With the advent of energy or impact-absorbing bumpers, automobile grilles have been required to undergo significant design changes in order to accommodate the stroke of the bumper, which can be as much as 3 to 4 inches. Current grille designs have followed primarily three approaches. The first and traditional approach is to position the grille entirely out of the path of the bumper during recoil after impact. This approach generally entails placing the automobile grille rearward of the bumper, resulting in an extremely square-looking profile which has little appeal according to modern design trends. In addition, such a design is not aerodynamic, and as such this approach is not generally followed, particularly as fuel efficiency becomes increasingly important.
A second approach is to completely eliminate the grille, which generally entails sweeping the engine hood down such that it is suspended just above the bumper line. However, this approach has not been widely adopted in that it has rather limited styling appeal.
A third approach is to require the grille to be displaceable such that it can pivot or otherwise move out of the bumper's path during impact. Preferably, this approach allows the grille to be mounted flush with the surrounding hood, front end body panels, and bumper so as to enhance the styling effect and aerodynamics of the automobile. Such an approach is illustrated by U.S. Pat. No. 3,792,889 to Fuener et al. During impact, the rearward travel of the bumper forces the grille to pivot rearwardly about the grille's lower edge and against a spring element. Another example of the third approach is taught by U.S. Pat. No. 4,753,468 to Szymczak et al., which provides a pivot arm which pivots the grille rearwardly and upwardly during impact. Yet another example is shown in U.S. Pat. No. 4,834,436 to Nguyen, which substantially eliminates the arcuate displacement of the grilles of both Fuener et al. and Szymczak et al. by employing a four-bar linkage that displaces the grille in an entirely rearward manner during impact. U.S. Pat. No. 4,944,540 to Mansoor et al. also seeks to avoid an arcuate path by the grille during impact by a pin and slot arrangement having a return spring.
As can be readily appreciated by those skilled in the art, the above examples corresponding to the third approach all entail additional hardware and space to accommodate the displacement of the grille. In addition, the added hardware is also necessary to adequately support the grille so as to be able to withstand wind resistance and road vibration while the vehicle is in use. But the additional hardware requirement itself is a disadvantage when it comes to both costs and weight from the standpoint of the vehicle manufacturer. The added costs entailed in purchasing and installing the above required hardware to achieve the desired results will generally be substantial, while the additional weight adversely affects the performance and fuel economy of the vehicle. Both considerations are of primary importance in the highly competitive automobile market.
An approach which tends to avoid the problems noted above is illustrated in U.S. Pat. No. 2,578,068 to Johnson. Johnson teaches a resilient grille and bumper combination which is resiliently attached at its lower edge to the automobile's frame. A more modern version of this approach is illustrated by U.S. Pat. No. 4,917,203 to Sacco et al. There, a grille is disclosed which is supported within a radiator cover. The radiator cover is secured to and suspended from the engine hood by resilient inner plates which allow the radiator cover to pivot elastically about the edge of the hood when the bumper is impacted. An advantage to the above structure is that the added hardware and weight associated with the teachings of Fuener et al., Szymczak et al., Nguyen, and Mansoor et al. are avoided. In addition, Sacco et al. particularly illustrate the styling and aerodynamic benefits to the automobile when the grille is mounted flush with the surrounding body panels and bumper.
However, the grilles taught by both Johnson and Sacco et al. have two significant disadvantages. First, the space requirements for the arcuate motion, recognized as being undesirable by Nguyen, are again present, such that a significant amount of space must be provided for the radiator cover to be displaced within the front end of the automobile. Second, the radiator cover can only be attached along one edge so as to allow the resilient pivotable movement between the radiator cover and the hood. As a result, the radiator cover is highly susceptible to wind and road vibrations, a clearly undesirable characteristic.
As a solution to each of the above disadvantages, U.S. Pat. No. 5,205,597 to Chase, assigned to the assignee of this invention, teaches an automobile grille which has the advantages of being able to deflect with the bumper during impact and being sufficiently supported by the automobile body, yet simultaneously avoids the need for added hardware and weight for purposes of providing these desirable capabilities. The solution taught by Chase involves modifying the internal structure of an automobile grille to provide a mode of resilience which enables the grille to absorb an impact with the bumper, while still being securely attached to the automobile body. In particular, Chase teaches a grille formed entirely from a resilient impact-resistant material, such as a high impact plastic, having a yield strength which is sufficient to endure the amount of deflection required to deflect with the bumper's stroke. The grille includes a generally elongated body portion which extends across a portion of the automobile's front end as determined by the automobile's particular design. The body portion has an upper edge which is preferably attached to the engine hood of the automobile, and a lower edge which generally extends horizontally adjacent to the bumper.
To provide the necessary deflection capability of the grille, at least the lower edge is formed to have a section modulus which varies along its length. Preferably, the section modulus of the lower edge has at least one locally reduced region so as to permit an enhanced degree of yielding without exceeding the yield strength of the material. As a result, the resiliency of the entire automobile grille is enhanced.
While the solution taught by Chase enables the automobile grille to flex significantly without sustaining permanent damage, the presence of a conventional decorative plating on such an automobile grille significantly increases the flexural modulus of the automobile grille. As used here, the term "flexural modulus" serves to quantify the suitability of a particular polymeric material for an application which requires a significant degree of flexing. Typically, articles made from such materials will be tested by flexing a test specimen at its center while being supported at two peripheral points. The flexural modulus indicates the stress-versus-strain relationship of the polymeric material, which serves as an indication of the ability of the article to be repeatedly flexed without becoming plastically deformed.
The presence of a decorative metallic coating, such as electroplated chromium, on an automobile grille dramatically increases the grille's apparent flexural modulus, at times by a factor of five or more. As a result, significantly less flexing is permitted for a given impact force. In the case where a grille is forced to deflect with an impact-absorbing bumper, the flexing required of the grille in order to accompany the bumper through its maximum stroke may plastically deform the grille and permanently damage the grille's decorative coating. Yet, such decorative coatings are highly desirable from an aesthetic standpoint, such that their elimination is not a viable solution.
Accordingly, what is needed is a flexible automobile grille which is provided with a decorative metallic coating, wherein the grille is capable of being rigidly attached to the surrounding automobile front end body panels and/or bumper, so as to withstand wind and road vibration, yet is also able to readily flex during impact or during the displacement of the bumper without incurring permanent damage to the physical structure of the grille or the grille's decorative coating.